Process of preparing hydrazine-ammonia addition compounds



Sept. 13, 1966 B. BERGHAUS ETAL 3,272,730

PROCESS OF PREPARING HYDRAZINE-AMMONIA ADDITION COMPOUNDS Filed Aug. 24,1964 INVENTOR Bern/Lard Berg/mus Maria Siaeso/ze ATTORNEYS United StatesPatent 3,272,730 PROCESS OF PREPARING HY DRAZINE-AMMONIA ADDITIONCOMPOUNDS Bernhard Berghaus, Zurich, and Maria Staesche, Wettingen,Aargau, Switzerland, assignors to Elektrophysikalische Anstalt BernhardBerghaus, Vaduz, Liechtenstein, a corporation of Liechtenstein FiledAug. 24, 1964, Ser. No. 391,387 13 Claims. (Cl. 204-177) Thisapplication is a continuation-in-part of application Ser. No. 27,212,filed May 5, 1960, now Patent No. 3,152,- 056, dated October 6, 1964.

The present invention relates to the synthesis of hydrazine-ammoniaaddition compounds and more particularly to such a synthesis by means ofan electrical jet discharge.

Hydrazine-ammonia addition compounds have not had anypreviouscomrnercial application. It was presumed, on the basis of thehigh exothermic heat to be expected on their reaction, thathydrazine-ammonia addition compounds would be particularly well suitedfor rocket propellants. The problem lying at the base of the presentinvention was, therefore, to find a convenient commercial process forpreparing hydrazine-ammonia addition compounds.

The process of preparing hydrazine-ammonia addition compounds accordingto the invention is carried out by conducting and subjecting a gascomprising nitrogen and hydrogen and consisting of one or more gases ofthe group consisting of ammonia, nitrogen and hydrogen, preferablyammonia alone, through a jetlike glow discharge, and subsequentlyseparating the reaction products, preferably by means of a cooling trapin which the hydrazine-ammonia addition compounds accumulate. The gascontaining nitrogen and hydrogen preferably consists of ammonia andhydrogen.

The gas comprising nitrogen and hydrogen is fed through a nozzle into areaction chamber, and the jetlike glow discharge is produced in the gasstream issuing from the nozzle. The latter preferably is connected as anelectrode of the glow discharge, suitably as the cathode.

Further, the process conveniently is carried out in a reaction vessel bymeans of one or more annular electrodes of which preferably one at leastis operated as anode of the glow discharge. The glow discharge suit-:ably is carried out at a gras pressure from 1 to 30 millimeters Hg,preferably from 2 to 6 mm. Hg, and at potentials from 200 to 400 v.Liquid air or liquid nitrogen is preferably used for cooling the coolingtrap.

The present invention is more clearly described with the aid of theapparatus for carrying out the process of the invention as shown in theaccompanying figure, which is a schematic representation of a suitablejet discharge reaction chamber and accompanying apparatus. In theapparatus shown, the reaction chamber 1 is enclosed on all sides bymetal walls 2 which are formed as doublewalls and adapted to receive acoolant which flows in the direction of the arrow 3 through theintermediate space 4. The top of chamber 1 is hermetically closed by acover 5 which is composed of electrically insulating material, andcarries annular feed means 6 made of metal of which the interior duct 7terminates in a nozzle 8 communicating with chamber 1. The wallenclosing the interior duct and the nozzle, is provided with coolantducts 9 and 10 through which flow a coolant such as water or liquid airin the direction from inlet 11 to outlet 12. The points of transitionfrom metal to insulating material on cover 5 are protected by slots 13,14 in a manner known per se.

In front of that portion of annular feed means 6 with nozzle 8 whichprojects into the discharge chamber, an electrical field is to beproduced. To such end a ring 15a is perpendicularly disposed ascounterelectrode immediately in front of nozzle 8 and is adjustablealong the nozzle axis, said ring being adjustably held by the interiorconductor of the insulated current inlet bushing 17a. The clear diameterof ring 15a which is coaxial to the nozzle axis is sufiicient to nothamper the gas jet issuing from the nozzle mouth. Ring 15a is connectedvia switch 16a to one pole of a voltage source 18 of which the otherpole is connected via a switch 16 to said feed means 6. Preferably adirect-voltage source 18 is used, of which the negative pole via switch16 energizes said means 6. On the other hand, one pole of a voltagesource 19, suitably a direct voltage source, is connected to switch 16a,which by a center tap via a switch 16b and a bushing 17b is connected toring 15b. The other pole of voltage source 19 is connected via a switchand a bushing 17c to ring 15c. It has proved of advantage to haveelectrode 15b positive with respect to electrode 15a.

The initial products are delivered to said inlet means perhaps togetherwith a carrier gas, through a line 21 that may be closed by a valve 20.If desired, the initial products may be mixed beforehand in a mixer 22.The pressure P in mixer 22 may be read from a manometer 26.

An outlet pipe 27 is connected to the lower end of reaction chamber 1which communicates via a shut-off valve 28 with an absorption unit 29ato which is connected a pump unit 29. Line 27 is so dimensioned thatchamber 1 and the mouth of line 27 may be maintained a predete1= minedpressure P that may be read from manometer 34. It is possible to raisethe pressure ratio P :P to high values. The hydrazine-ammonia additioncompound a) cumulates in the absorption unit 29a which is a cooling trapcooled by liquid air or other suitable means.

An essential feature of the present process is the fact that a jetlikeglow discharge 36 is maintained in cham-- her 1. To such end, a pressureP of suitably 1 to 30 millimeters Hg, preferably from 2 to 6 mm. Hg, isproduced in chamber 1 and maintained at least in the immediate vicinityof the mouth of line 27, and simultaneously a gas stream is introducedunder a pressure P through the nozzlelike opening 8 in said feed means6. By suitably balancing the pressure P at the mouth of nozzle 8, andthe pump performance on line 27, and by a compatible adjustment of theclear width of the nozzle, a steady state is obtained in which prevailsa pressure difference (P -P in the reaction chamber between the mouth ofnozzle 8 and the outlet line 27. Thereby, the entering gas stream thenassumes at the mouth of nozzle 8 the form of a high ion density gas jetthe exact configuration of which may be varied depending on the nozzleshape. In FIG. 1 a jet that is essentially spheroidal with respect tothe nozzle axis, is schematically indicated by the dotted lines 36, butthe radial extent of the spindlelike limiting surfaces is exaggerated incomparison with the actual shape for the sake of clarity. Further andfor the same reason, the deformations of the jet which mostly ariseimmediately at the mouth, are not shown. When the gas stream spreadsfreely in chamber 1, the individual gas particles will pass over themajor portion of the distance between nozzle opening 8 and thecounterelectrodes 15 at high velocity. By a suitable choice of the totalpressure head (P P the velocity and thus also the flow time of thereactants may be adjusted within wide limits to the desired value.

Inside the jet, a luminous phenomenon develops from the ordinary glowappearance, mostly in the form of an illuminating ray of which thestructure is different from all the gas and glow discharge phenomenaknown so far. The appearance and shape of the illuminating zoneapparently is determined by the gas jet, but occasionally there is alsoobserved a stratification within the luminous phenomenon. The spectralrange of the light-emission is determined to a certain extent by thereactions taking 3 place in the ray or jet. In this connection, thelightemitting regions in the jet are not, of course, the sole spaceportions which can energize reactions, as the reaction zone proper alsomay comprise non-luminous portions of the jet as well as the immediatevicinity thereof and may extent into nozzle opening 8.

The shape of the reaction zone is governed to a high degree by the flowvelocity of the jet, although the reaction zone does not have to extendentirely across the same. An essential feature of the present form ofdischarge is the sharp demarcation thereof from its surroundings, whichmay be due to the steep pressure drop \from jet core to jet rim. Since,according to the Well-known relationship in which the energy turnover ofgas discharges increases with the gas pressure in an approximately cubicfunction, and further, since the pressure at the jet rim is already theprevailing pressure P of the vessel, one may safely assume that thereaction is most vigorous in the interior of the jet wheresimultaneously the maximum ion density at relatively low temperature ispresent. In accordance with all observed experience, the reactants arealready dissociated by the electrical action shortly after leavingnozzle 8. The reaction of the individual ions takes place during theirpassage through jet 36.

The length of time in which the reactants remain in the jet, normallylies in the range from fractions of milliseconds to fractions ofseconds. This short, reg-ulable duration of action of the electric fieldand the fact already mentioned that the reactants leaving the jet moveat once into a space sector which is at another pressure and perhapsalso at another temperature, is considered the reason for the surprisingchemical eifect of the present process.

When pure ammonia is supplied through nozzle 8 into the apparatusdescribed above, and when the resulting products are cooled in liquidair, non-decomposed NH and a liquid is recovered on thawing which meltsat about 20 C. and smells intensively like ammonia but which gives thehydrazine reaction with p-dimethylaminobenzaldehyde. Said liquid slowlyvolatilizes at room tem peratures and more quickly at +30 to 40 C., butin either case is completely volatilized. In the fresh state, saidliquid develops a high gas pressure.

Said liquid also is formed by the reaction of a mixture of H and N andof mixtures of NH and N or NH and H or NH and H and N The liquidcomprises the desired hydrazine-ammnoia addition compounds whichcorrespond to the general formula N H -nNH where n is the number ofammonia molecules added to a hydrazine molecule. It was found thathydrazine-ammonia additive N H -4NH preferably is formed in which, n is4 in this case. Also recovered, however, were a series of other suchaddition compounds where It varies from 1 to 20.

The hydrazine-ammonia addition compounds prepared in accordance with theprocess described above, on account of their exothermic heat andrelatively low specific weight, are very suitable for rocket propellantsin particular as substitute for pure hydrazine still used today. Ascompared with the latter, the exothermic heat and the volume of theadditives prepared according to the present process are much morefavorable at comparable weights.

The invention is illustrated, but not limited, by the following specificexample of preparation of hydrazineammonia addition compounds.

Example An apparatus similar to that shown in FIG. 1 was used,comprising a water-cooled feed means 6 having a nozzle bore of abt. 1mm. clear width. Pure NH gas was supplied to nozzle 8 through valve 20and line 21, and injected as a jet into reaction chamber 1. The pressurein the latter was first adjusted to P =1 millimeter Hg, the switches 16,16a then closed, and the regulable direct-voltage source 18 adjusted insteps from 200 v. to higher values until the field intensity between thecathodic nozzle 8 and the anodic counterelectrode 15a was suflicientlyhigh and there appeared a gas or glow discharge between nozzle mouth andcounterelectrode. There was formed a jet about 1 meter long whichemitted a brightly bluish and reddish light. By adjusting the pumpperformance and the pressure in line 21, the gasthroughput then wasadjusted to 3 liters per minute, pressure P being about from 20 to 30mm. Hg. The voltage across current source 18 then was abt. 340 v. andthe wattage from 300 to 400 w., mostly from 350- 360 W. The intenselyluminous jet could be maintained for any length of time with theseadjustments.

Now the cooling device, comprising 2 tubes of 200 mm. leg length and 20mm. diameter, was immersed in liquid air and removed therefrom after 10minutes. After distilling-off the NH there were recovered in the firsttube 1.29 grams and in the second tube 0.20 gram, or a total of 1.49grams of a liquid melting at 20 C., which liquid according to theanalysis comprised addition compounds of ammonia and hydrazine.

-It should be understood of course that the foregoing disclosure relatesonly to a preferred embodiment of the invention and that numerousmodifications, additions or alterations may be made therein withoutdeparting from the spirit and the scope of the invention as set forth inthe appended claims.

What we claim is:

1. A process for the production of addition compounds of hydrazine andammonia comprising subjecting a gas selected from the group consistingof (1) ammonia and (2) at least two gases of the group consisting ofammonia gas, nitrogen and hydrogen to an electric glow discharge in theform of a jet discharge to form a reaction mixture containing additioncompounds of hydrazine and ammonia and removing the formed reactionmixture rapidly from said discharge zone.

2. A process according to claim 1 in which the addition compounds are ofthe formula N H -nNH where n is an integer from 1 to '20.

3. A process according to claim 2 in which n is 4.

4. A process according to claim 1 in which the hydrazine-ammoniaaddition compounds are separated from the reaction mixture by cooling.

5. A process according to claim 1 in which the gas comprises ammonia.

6. A process according to claim 5 in which the gas comprises ammonia andhydrogen.

7. A process according to claim 1 in which the reaction is conducted ata pressure of 1 to 30 mm. Hg.

8. A process according to claim 7 in which the pressure is 2 to 6 mm.Hg.

9. A process according to claim 1 in which the potential differenceacross the current source of the discharge is from 200 to 400 volts andthe power from 300 to 400 watts.

10. A process according to claim 9 in which the potential difference is340 volts and the power 350 to 360 watts.

11. A process for the production of an addition compound of hydrazineand ammonia comprising introducing at high velocity under pressurethrough a metallic nozzle shaped restricted inlet into a reaction zoneat reduced pressure a member selected from the group consisting of (l)ammonia gas and (2) at least two gases of the group consisting ofammonia gas, nitrogen and hydrogen, generating an electric glowdischarge in said introduced gas in the form of a jet dischargeradiating into the reaction zone axially from said metallic nozzle asone electrode toward an area of lower pressure and an electrode ofopposite polarity disposed in said reaction zone to form a reactionmixture containing addition compounds of hydrazine and ammonia; removingthe formed reaction mixture rapidly from said zone and separating theaddition compound of hydrazine and ammonia from the withdrawn reactionmixture.

12. A process according to claim 11 in which the restricted inlet has aclear width of about 1 mm.

3,272,730 5 6 13. A process according to claim 11 in which the OTHERREFERENCES metallic nozzle electrode is cathodic.

Journal of Physical Chemistry, vol. XXXVII, N0. 7 References Cited bythe Examiner (1933), pages 899-901.

UNITED STATES PATENTS 5 JOHN H. MACK, Primary Examiner. 3,003,06110/1961 Berghaus et a1. 2043 12 X 3,020,223 2/1962 Manion 204-477 HOWARDS. WILLIAMS, Examiner.

1. A PROCESS FOR THE PRODUCTION OF ADDITION COMPOUNDS OF HYDRAZINE ANDAMMONIA COMPRISING SUBJECTING A GAS SELECTED FROM THE GROUP CONSISTINGOF ((1) AMMONIA AND (2) AT LEAST TWO GASES OF THE GROUP CONSISTING OFAMMONIA GAS, NITROGEN AND HYDROGEN TO AN ELECTRIC GLOW DISCHARGE IN THEFORM OF A JET DISCHARGE TO FORM A REACTION MIXTURE CONTAINING ADDITIONCOMPOUNDS OF HYDRAZINE AND AMMONIA AND REMOVING THE FORMED REACTIONMIXTURE RAPIDLY FROM SAID DISCHARGE ZONE.